I don't recall a statement by the student stating she agreed to the rules. You are merely invoking what the teachers said she agreed to. There might be another side to the story. Perhaps the student realized the intolerance the teachers had for free and harmless speech and so she chose to speak her own mind instead of the teachers'.
Thanks. That clears it up. The teacher is lying and the student, in a sudden blinding flash of clarity, decides to disobey what are obviously bad rules. In fact, the rules are so hideously bad and immoral that she has no choice but to violate them without discussing them with anyone, least of all the teacher...
Government actors can't make rules that break the Supreme Law of the Land.
You think you have the wherewithal to understand that?